One conventional image forming apparatus provided with a position correction function to correct an image formation position for forming an image on a sheet has the following structure (see Japanese Patent Application Publication No. 2008-225192). This conventional image forming apparatus has an image forming device, a conveying body, and a sensor. The image forming device forms a mark for position detection on the conveying body. The sensor detects the position of the mark. The image formation position is corrected based on the position of the detected mark.